As November opens, Comet ISON MIGHT have brightened to naked eye visibility, or it might not quite have reached that level of brightness yet. It should certainly be visible with a pair of binoculars to anyone who goes to a site with a dark sky unspoiled by light pollution This will be the most exciting time of the whole apparition I think, as each day more and more people get to see it.

Having said that, ISON will STILL be a pre-dawn object, so it will only be visible to people who either get up early or stay up late, i.e people who make a real, concerted effort to see it. Seeing it will still mean getting up before dawn, but if the comet is on track to become a Great Comet then it will definitely be worth it, because by now it shouldn’t need “finding”, it should just be THERE in the sky if you look to the brightening eastern sky before dawn. Of course, it’s possible that ISON will decide to let us all down and fizzle out, we can’t dismiss that possibility. But even if that happens it will still be worth looking for, and these images will help you find it. But let’s be optimistic! Let’s assume ISON behaves itself and doesn’t sputter out, and is a decent naked eye comet. Where will it be..?

As I said, until the very final days of November, the comet will be in the MORNING sky… Looking east at around 5am (UK time, yours will differ if you’re not in the UK, obviously!) on Nov 1st (below) you’ll see this scene: the comet shining close to Mars, with a beeyootiful thin crescent Moon beneath it, and Jupiter shining off to its upper right. I wonder how long ISON’s tail will be at this point…?

On that subject, please note, YET AGAIN, that the tails shown in these images should NOT be taken as accurate, for either their length or brightness. They were generated by planetarium software which can’t accurately predict WHAT a comet’s tail will look like, so just use these images to guide you to WHERE to look at the times given, and take the appearance of the tail on the images with a large pinch of salt, ok?

Reports of naked-eye sightings of Comet ISON are coming in from around the world. Experienced observers put the comet's magntitude at +5.5 on Nov. 16th. This means it is now fully 10 times brighter than it was only three days ago before the outburst. To the naked eye, ISON appears as a faint smudge of pale green light low in the pre-dawn sky. The view through a telescope is more dramatic. The comet's tail has become a riotous crowd of gaseous streamers stretching more than 3.5 degrees across the sky. Amateur astronomer Waldemar Skorupa sends this picture from Kahler Asten, Germany:

The tail is so long, he couldn't fit the whole thing in the field of view. How long is it? Comet ISON's tail extends more than 8 million kilometers behind the comet's nucleus. For comparison, that's 21 times the distance between Earth and the Moon.

Because so much gas and dust is spewing from the comet's core, it is impossible to see clearly what caused Comet ISON's outburst on Nov. 13-14. One possibility is that fresh veins of ice are opening up in the comet's nucleus, vaporizing furiously as ISON approaches the sun. Another possibility is that the nucleus has completely fragmented.

"If so, it will still be several days before we know for sure," says Karl Battams, an astronomer with NASA's Comet ISON Observing Campaign. "When comet nuclei fall apart, it’s not like a shrapnel-laden explosion. Instead, the chunks slowly drift apart at slightly different speeds. Given that ISON’s nucleus is shrouded in such a tremendous volume of light-scattering dust and gas right now, it will be almost impossible to determine this for at least a few days and perhaps not until the comet reaches the field of view of NASA's STEREO HI-1A instrument on November 21, 2013. We will have to wait for the chunks to drift apart a sufficient distance, assuming they don't crumble first."

In short, no one knows for sure what is happening to Comet ISON. This could be the comet's death throes--or just the first of many brightening events the comet experiences as it plunges toward the sun for a close encounter on Thanksgiving Day (Nov. 28th).

Monitoring is encouraged. Comet ISON rises in the east just before the sun. Amateur astronomers, if you have a GOTO telescope, enter these coordinates. Dates of special interest include Nov. 17th and 18th when the comet will pass the bright star Spica, making ISON extra-easy to find.

I’m getting quite a few questions from people wondering if they can see Comet ISON from where they live, which is nice because it means my blog is reaching people in lots of different countries and not just in Europe or the US. If you are one of the people wondering if you can see ISON from your part of the world, this page is for you…

Before anything else, what I recommend is downloading an astronomy App for your smartphone. Whether you have an Android or an IPhone, there are now several Apps which you can download, for free, which will tell you and show you exactly when and where you will be able to see ISON from where you live. There’s a whole page of this blog dedicated to them – and to other ways of finding the comet – and you’ll find it on the menu at the top of the page. The one I recommend above all others is called SKY SAFARI. I swear by it (or at it, sometimes, if the screen shows me where ISON is but the sky is cloudy…!)

Of course, lots of people don’t have a smartphone, so what do you do if you’re one of them? Well, a good place to start is with this fantastic chart, created by the Hubble ISON blog team. It splits the world into banded zones, and tells you when ISON will be visible from each band. Simple!

Comet's ISON's recent outburst of activity has done more than simply brighten the comet. Whatever exploded from the comet's core also created a spectacularly-long tail, more than 16 million kilometers from end to end. Scroll down to see the full extent of Comet ISON as photographed on Nov. 17th by Michael Jäger of Ebenwaldhöhe, Austria:

"The tail of the comet stretches more than 7o across the sky," says Jäger. It's almost as wide as the bowl of the Big Dipper.

Physically, ISON's tail is about 12 times wider than the sun. So, when the head of ISON plunges into the sun's atmosphere on Nov. 28th, more than 15 million kilometers of the comet's tail will still be jutting into space behind it.

Because so much gas and dust is spewing from the comet's core, it is impossible to see clearly what caused Comet ISON's outburst on Nov. 13-14. One possibility is that fresh veins of ice are opening up in the comet's nucleus, vaporizing furiously as ISON approaches the sun. Another possibility is that the nucleus has completely fragmented.

"If so, it will still be several days before we know for sure," says Karl Battams, an astronomer with NASA's Comet ISON Observing Campaign. "When comet nuclei fall apart, it’s not like a shrapnel-laden explosion. Instead, the chunks slowly drift apart at slightly different speeds. Given that ISON’s nucleus is shrouded in such a tremendous volume of light-scattering dust and gas right now, it will be almost impossible to determine this for at least a few days and perhaps not until the comet reaches the field of view of NASA's STEREO HI-1A instrument on November 21, 2013. We will have to wait for the chunks to drift apart a sufficient distance, assuming they don't crumble first."

Monitoring is encouraged. Comet ISON rises in the east just before the sun.

Comet ISON is plunging toward the sun and brightening as it heads for a perilous close encounter on Nov. 28th. This morning, with the "final countdown" clock at T-7 days, Juan Carlos Casado photographed the sundiver over the Teide Observatory in the Canary Islands:

"The comet is over the distant island of Gran Canaria," he says, "while in the central cloud we can see the planet Mercury. ISON was at the limit of naked-eye visibility, but it was an easy target for my SLR camera with a small telephoto lens (85 mm focal length) on a static tripod and 6 seconds of exposure."

Because Comet ISON is moving into the rosy glow of dawn, it will soon be impossible for cameras on Earth to track it. NASA's fleet of solar spacecraft are about to take over. Later today, Comet ISON will enter the field of view of the STEREO-A spacecraft. The Heliospheric Imager on STEREO-A will pick up the comet just as Earth-bound telescopes begin to lose it. In the days that follow, STEREO-B, SOHO and the Solar Dynamics Observatory will join the hunt, providing continuous views of Comet ISON all the way to perihelion (closest approach to the sun) on Nov. 28th. Stay tuned!

Because NASA's twin STEREO probes are designed to observe the sun, they can see sundiving comets even when the glare becomes intense. Yesterday, Comet ISON joined Earth, Mercury, and Comet Encke in the field of view of STEREO-A's Heliospheric Imager. Click on the image to view ISON's grand entrance:

"The dark 'clouds' of stuff you see coming from the right are density enhancements in the solar wind, and these are what are causing all the ripples you see in comet Encke's tail," explains Karl Battams of NASA's Comet ISON Observing Campaign. "I can pretty much promise you that we're going to see ISON's tail doing that in a couple of day's time, but on a much larger scale!"

Battams points out another exciting development: Comet Encke and Comet ISON are converging for a photogenic close encounter. "No they're not going to hit each other - in reality they are millions of miles apart - but as seen from the STEREO-A spacecraft, they are going to get very close!" he says. "We are probably a couple of days away from seeing two comets almost side-by-side in that camera, with long tails flowing behind them in the solar wind. To say that such an image will be unprecedented is rather an understatement." Stay tuned for that.

Comet ISON is now only 5 days from perihelion. On Nov, 28th, Thanksgiving Day in the USA, it will fly through the sun's atmosphere little more than a million kilometers above the surface of the sun. At closest approach, the temperature of ISON's core could rise as high as 5000o Fahrenheit--an existential challenge for an icy comet. No one knows if it will survive.

As the "final countdown" ticks to zero, photographers are taking some marvelous parting shots. Here is Comet ISON plunging into the sunrise beside Mt. Fuji on Nov. 22nd:

Japanese photographer Kagaya took the picture using a Canon EOS 1D C digital camera. "This is a 3-second exposure at ISO 2000," he says. In the full-sized image, you can also see Mercury hovering to the left of the comet.

NASA's STEREO-A spacecraft is monitoring Comet ISON as it approaches the sun for a close encounter on Nov. 28th. The latest movie from the spacecraft's Heliospheric Imager captures not only Comet ISON but also Earth, Mercury, and Comet Encke. Click to set the scene in motion:

In the movie, which spans a two day period from Nov. 19 to Nov. 22, the sun is to the right, off-screen. "The dark 'clouds' coming from that direction are density enhancements in the solar wind, and these are what are causing the ripples you see in the comet tails," explains Karl Battams of NASA's Comet ISON Observing Campaign.

Although the two comets seem to be experiencing the same solar wind, their tails ripple differently. "Encke has kind of long waves in the tail, whereas ISON's seems almost like high-frequency puffs," points out Battams.

Appearances notwithstanding, the two comets might be in two different streams of solar wind. "The most likely explanation is that ISON is in a faster stream," he comntinues. "Imagine holding a flag on a slightly breezy day. The flag will waft gently in the breeze. Now imagine holding it in really strong winds. The flag will be rippling violently, but those ripples will be smaller in amplitude."

As Comet ISON approaches the sun, it is becoming increasingly difficult for observers on Earth to photograph the comet. Indeed, by Nov. 24th it seemed impossible. But it only seemed that way. Working from a high-altitude site in the Canary islands, Juan Carlos Casado successfully imaged Comet ISON on Sunday morning deep inside the rosy glow of dawn:

I took this picture of Comet ISON on Nov. 24th at 6: 25 UT from the Teide Observatory," says Casado. "The comet was over the distant island of Gran Canaria above a sea of clouds about 1 hour before sunrise and only 16° from the sun. The exceptional atmospheric conditions of Teide Observatory allowed me to capture the image."

Could this be the last clear photo of Comet ISON taken from Earth? No one knows.

On November 28, 2013, the SDO (Solar Dynamics Observatory) spacecraft will off-point at three different positions as Comet ISON moves through perihelion. This website will display near realtime images and movies of this sungrazing comet. Images should begin appearing sometime between 12:45 pm and 1:00 pm ET.

Comet ISON is getting all the press, but there is a second comet near the sun as well: Comet Encke. NASA's STEREO-A spacecraft is monitoring both. Click to view an updated movie of the solar wind buffeting two comets:

In the movie, which spans a three+ day period from Nov. 20 to Nov. 23, the sun is to the right, off-screen. At first glance, Earth and Mercury appear to be labeled backwards. The strange arrangement is actually correct. This is how the two planets appear from STEREO-A's vantage point over the farside of the sun.

"The dark 'clouds' moving from left to right are density enhancements in the solar wind, and these are what are causing the ripples you see in the comet tails," explains Karl Battams of NASA's Comet ISON Observing Campaign.

The ripples could become even more dramatic if a CME hits the comets. This is Comet ISON's first visit to the sun, but Comet Encke has been here before. In 2007 a CME hit Encke and ripped off its tail. Battams and other researchers hope something similar is about to happen now. "I'd love to see a big CME hit Comet ISON," he says in a story from Science@NASA. Watching the impact could teach researchers new things about CMEs and comets.